Repairing the Yoke

The ends of the yoke are rotted, but the main part is still perfectly serviceable.
The ends of the yoke are rotted, but the main part is still perfectly serviceable.

The yoke is a thwart (cross piece) at the balance point of the canoe that you can rest on your shoulders when you’re portaging (carrying) the canoe.  This canoe’s yoke is made of Ash, a good hard, but rot-prone wood.  Baseball bats are made of Ash too.  At any rate,  since the main part of this beautifully carved yoke is still perfectly serviceable, an easy fix is to scarf on new ends.  Check out my previous article here more about scarf joints. Continue reading “Repairing the Yoke”

The Board Stretcher a.k.a The Scarf Joint

Finished Scarf Joint
Finished Scarf Joint

What do you do when you can’t get lumber long enough to fill the need?  You go get the board stretcher!  Any neophyte woodworker has heard that one.  But the board stretcher I’m referring to really does exist.  It’s called a scarf joint.

Boatbuilders have been scarfing together lumber for a long time.  It’s a method of joining two boards so they have continuous sides as if the two boards have grown together to form one long board.  Before the days of the great glues we have today, the scarf joint was made by overlapping the boards with a long diagonal cut, and then pegging a backing block to the joint.  But I’m using epoxy.  And if done properly, the glued scarf joint is stronger than the wood fibers themselves, obviating the need for a backing block.

In this case, I’m scarfing together two planks to make a blank that is 16 ft. long by 6 inches wide by 1-1/2 inches thick.  That’s a serious piece of white oak!  But it needs to be, it’s the backbone of the boat.

So I start with an 8 ft and a 10 ft plank.  The scarf joint will be a diagonal overlap at a 12:1 ration.  This means that since the planks are 1-1/2 inches thick, the joint will be 18 inches long.  The joint needs to be so long in order to provide plenty of faying (glue-able) surface.  The more faying surface, the stronger the joint.  A structural joint like this one requires a 12:1 ratio.

1. Lining out the scarf cut on the edge of the board.
1. Lining out the scarf cut on the edge of the board.

I first line out the part of the board that will be cut away.  Look closely in the picture at left, and you’ll see the diagonal line I’ve drawn on the edge of the board.

 

 

 

 

 

 

 

2. Boards stacked ready for planing.
2. Boards stacked ready for planing.

Then I stack the two boards on top of each other, offsetting them so I can make one long slanted cut with the power plane at the angle I want.  I finish the cut with the hand plane to make for a good fit.

 

Finished scarf cut.
3. Finished scarf cut.

 

 

 

4. Scarf joint wet out with epoxy.
4. Scarf joint wet out with epoxy.

 

 

 

 

Then wet out the glued surfaces with straight epoxy.  This lets some of the epoxy soak into the pores of the wood so the joint won’t be starved of glue.  Then slather on a nice thickened mixture of epoxy and clamp, leaving overnight for it to partially cure.

 

5.  Clamped scarf joint.
5. Clamped scarf joint.

When the joint is set, but the epoxy is still “green”, it’s time to plane it down to the finished thickness and clean up the joint.

 

 

 

6.  Laying out the outline of the finished keel on the new blank with a batten.
6. Laying out the outline of the finished keel on the new blank with a batten.

Then lay out the outline of the new blank from measurements taken from the old keel.  Since the edges are a curved taper, they have to be lined off with a batten as shown in the photo.

 

 

 

Finally, the blank is cut out on the bandsaw.  And there it is.

7.  The finished blank is cut out on the bandsaw.

7. The finished blank is cut out on the bandsaw.

The next step is to cut the rabbet (the groove along each edge where the bottom planking rests.  That’s another story…